Thrust spring

ABSTRACT

An elastomer spring for supporting an axially arranged coil spring, in particular in an engine mounting is constructed to reduce the radial loads on the coil spring with simultaneous damping and includes a transversely soft composition for the elastomeric spring. The elastomeric spring is provided with a centering projection which may be introduced into the coil spring and a section which may be deformed by the effect of radial forces, with a molded sheet being provided to stabilize the force carrying section of the elastomeric spring.

[0001] The invention relates to an elastomer spring for supporting anaxially aligned helical spring in series connection, with said helicalspring being axially loadable as provided under static and dynamicpressure.

[0002] The invention particularly relates to an elastomer spring forsupporting that type of helical springs consisting of spring steel.

[0003] Helical springs made of spring steel exhibit excellentproperties, in particular when being used for absorbing dynamic pressureloads. They allow for long linear spring excursions even when acted uponwith dynamic load and also demonstrate a surprisingly good stabilityunder such loads, are hard-wearing and inexpensive and haveself-resonance ranges in comparatively high frequencies due to their lowabsorption factor. When used in conventional dynamically loaded bearingsfor machine units, such helical steel springs achieve several millionsof load alternation cycles without functional failure with linear axialresilience paths of 20%. Insofar, they are to be considered as beingideal components for the automobile bearing construction. The reason whysuch helical steel springs are in fact hardly being used to date in theconstruction of unit bearings for the construction of cars, resides intwo almost insuperable disadvantageous properties of these springs,namely in their only extremely low stability under radial load, and intheir excellent, yet absolutely undesired good conductivity ofstructure-borne noise. With respect to their mechanical strength,helical steel springs can be described as having a perdurable stabilitywith axial load, but when being subjected to only a minor radial load,they have, at best, a short-term stability.

[0004] It is known from prior art, such as for example from the twoGerman laid-open documents DE 195 34 239 A1 and DE 23 07 567 A1, thatnumerous attempts have been made to prevent the two unfavorableproperties of helical steel springs identified above from becomingeffective, in which the helical steel spring disposed in the bearing asa suspension spring is mounted on rubber cushions in three dimensionsand is buffered by a rubber coating pad extending axially to the helicalspring. The bearing properties, however, could not be thus improved,since the rubber cushions under and on the helical springs wore outrapidly due to the high dynamic stress introductions, and the relieffrom transverse forces in the helical spring was not efficient enough.

[0005] Starting from said prior art, the invention is based on thetechnical object of realizing an elastomer spring for supporting anaxially aligned helical spring which is also axially loadable asprovided under static and dynamic pressure, with said helical springachieving sufficient permanent stability, even when used in bearingsexposed to major transverse forces in the radial direction withappropriate load.

[0006] The invention solves this problem in that said elastomer springfor supporting the helical spring is, matched by way of configurationand dimensioning to the parameters of use given in each case, configuredand dimensioned laterally yielding, i.e. in the radial direction,relative to the axially aligned helical spring to be supported, andhaving, in the radial direction, a markedly low spring rigidity.

[0007] In contrast to prior art, the concept on which the invention isbased does not reside in compensating the effects of impingingtransverse forces by axially stabilizing the helical spring through thecapture of the helical spring in a constructional-mechanical manner orthrough the over-dimensioning of same. It is rather that the helicalspring is supported on an elastomer spring, which is matched as aparticularly laterally yielding transverse load spring. The transverseforces arising between the bearing and the counter-bearing in such aspring arrangement are thereby entirely absorbed in the laterallyyielding transverse load spring, the spring rigidity of which, in theradial direction, is smaller by a multiple than the spring rigidity ofthe helical spring in the radial direction. Thus, it is achieved thatthe transverse forces or shearing forces acting upon such a springarrangement can virtually be entirely decoupled from the axial helicalspring.

[0008] The elastomer spring used for supporting the helical spring hasto be correspondingly so non-rigidly adjusted in the radial plane thatit is able to absorb all transverse forces in a resilient and decouplingmanner, which by far might even come close to the critical radial loadcapacity of the helical spring. However, it is to be designed asresistive to transverse loads as possible within observation of thislimit, so as to prevent the supported helical spring from anuncontrolled floating.

[0009] The method of realizing such a matching of the radial springrigidity of a laterally yielding transverse load spring is, inprinciple, possible for every person skilled in the art of rubbertechnology. Preferably, the spring rigidity of the elastomer springserving as a transverse load spring is here reduced in that the axialheight of the elastomer spring is increased, the hardness of the matrixelastomer of the transverse load spring is decreased, and, in particularwhen a higher elastomer hardness is chosen for the purpose of mechanicalstability, recesses and cavities in the matrix are incorporated intosuch a type of material-wise harder elastomer matrix. In this way, theratio of axial rigidity/radial rigidity of the series connection of thehelical steel spring and the transverse load absorbing elastomer springcan be set to values ranging from 1:1 to 30:1. As a rule, an operationrange of this ratio of axial rigidity/radial rigidity is therebypreferably to be set from 10:1 to 20:1.

[0010] According to a configuration of the invention, a profiled sheetmetal is incorporated by vulcanization into the elastomer springimmediately below the load-receiving surface of the elastomer spring,plane-parallel to same and completely enclosed by the elastomer of thespring, the surface of said profiled sheet metal being complementary inshape to the supporting surface of the helical spring and being therebydimensioned at least slightly larger than said force-introducingsupporting surface of the helical spring. The elastomer layer betweenthe surface of the profiled sheet metal and the supporting ring surfaceof the lowest winding of the helical coil is thereby in principle assmall as possible, but has to be sufficiently large at the same time soas to withstand a permanent mechanical stress and also to acousticallyisolate the helical spring with respect to the introducedstructure-borne noise as early as in this place.

[0011] Such a kind of radially aligned disc, namely a profiled sheetmetal incorporated by vulcanization, provides for a stable and widesurface, hence mostly tension-free introduction of the forces introducedinto the elastomer spring by the helical spring. The profiled sheetmetal hence serves for an improvement of the mechanical coupling of thesupported helical spring to the laterally yielding elastomer spring.

[0012] According to a further configuration of the invention, thedynamic connection of the helical spring to the elastomer spring can befurther improved in that on the load-receiving surface of the elastomerspring, a dome is formed projecting axially into the helical spring,which is homogenously formed as a rule, at the same time when the springelastomer is injection-molded. The coupling can in particular still befurther improved in that the profiled sheet metal of the load-receivingsurface is also pulled into said dome and hence also into the base ofthe helical spring, in a cylindrical or a parallelepiped shape orprincipally with a ground surface configuration matching the helicalspring. Also the profiled sheet metal thus spatially expanded, is ineach case completely incorporated into the elastomer of the dome and thespring by way of vulcanization.

[0013] A quite essential stabilization and improvement of the entiredevice can moreover be achieved by a further configuration of theinvention in that the bottom face opposite the load-receiving surface ofthe elastomer spring does not rest directly on a connection piece of thecounter-bearing or is inserted in a receiver formed therein in ashape-complementary manner, but is rather connected all-over and in amaterial-fitting manner with a profiled sheet metal-type bottom plate.Said bottom plate, being interconnected mechanically fix all-over and ina material-fitting manner with the elastomer spring by adhesion,incorporation by vulcanization, can then be inserted or placed on top ofa correspondingly configured counter-bearing connection piece of abearing or an otherwise configured receptacle preferably in aform-fitting manner or at least form-fittingly fixed in the radialplane. Such a kind of a mostly form-fitting connection of the transverseload elastomer spring to the counter-bearing, for one, and to the baseof the supported helical spring, for another, guarantees an optimallyreproducible introduction of emerging transverse force components intothe laterally yielding elastomer spring. It is moreover guaranteed bythe thus ensured homogenous introduction of the emerging axial forcesvia the two profiled sheet metals into the transverse load spring thatin the manner inherent in the material rubber, the transverse rigidityof the elastomer spring decreases with increasing axial load. Thisresults additionally in a safety tolerance even in the limit range ofthe respective dimensioning and configuration of the spring system.

[0014] Due to the series connection of a helical spring steel spring andthe laterally yielding elastomer spring, bearings can be producedexhibiting optimum characteristic rating data fields when these bearingsare used as unit bearings in a motor vehicle.

[0015] Further configurations of the invention are the subject matter ofthe subclaims and are explained in detail in the following by means ofrealization examples in conjunction with the drawings.

[0016] It is shown in

[0017]FIG. 1 a first example of a realization of the invention in anaxial section and a schematic representation; and

[0018]FIG. 2 a second example of a realization of the invention,likewise in an axial section and a schematic representation.

[0019] In FIG. 1, a first example of a realization of the invention isshown in an axial section and in a mostly schematized representation. Onan elastomer spring 1, the base 4 of a helical spring 2 made of springsteel, is supported. The bottom face 5 of the elastomer spring 1 issupported on a counter-bearing 3. The load-receiving head 6 of thehelical spring 2 carries a dynamically load-impingible bearing 7.

[0020] On the load-receiving surface 8 of the elastomer spring 1, a dome9 is integrally formed from the matrix elastomer of elastomer spring 1.The outer contour of dome 9 is so adapted to the clear inner contour ofhelical spring 2 that dome 9 acts as a centering pin for helical spring2 on the load-receiving surface 8 of elastomer spring 1.

[0021] Closely below the surface of elastomer spring 1 on theload-receiving side, and following the entire three-dimensional contourthereof in a plane-parallel manner, a profiled sheet metal 10 is soincorporated into elastomer spring 1 by vulcanization that the sheetmetal is completely enclosed by the elastomer. So as to ensure apermanent and hard-wearing integration of the sheet metal, in spite ofthe surface-close position of the sheet metal 10 in the elastomer ofelastomer spring 1, the plane, annulus-shaped outer area of sheet metal10, is provided with recesses 11 through which the elastomer ofelastomer spring 1 extends.

[0022] The matrix elastomer of elastomer spring 1 is set in the rubbermixture and, if necessary, by realizing additional recesses (cf. FIG.2), to be so laterally yielding that upon occurrence of transverse forcecomponents 12 under load 13 in the series-connected spring systemconsisting of elastomer spring 1 and helical spring 2, all transverseforces are absorbed in the laterally yielding elastomer spring 1 actingas a transverse load spring, and hence, helical spring 2 is decoupledand therewith protected from the occurrence of service-life-shorteningtransverse force components. In FIG. 2, this transverse force decouplingis illustrated by the dashed lines 3′ and 1′.

[0023] A further example of elastomer spring 1 is shown in the assemblyof a schematically illustrated typical motor bearing for a motorvehicle.

[0024]FIG. 2 shows the inventive elastomer spring 1 built into a motorbearing 14 together with a helical spring 2, in a cut representation.Motor bearing 14 is only partially shown in FIG. 2 and can be recognizedby a bearing connection piece 7, as well as a lower housing wall servingsame as a counter-bearing 3.

[0025] In bearing connection piece 7, a central bore 15 including athread is provided as a bearing connection for connecting a load, whichcentral bore is open on the bearing side, and closed in a fluid-tightmanner towards the hydraulic bearing on the counter-bearing side.

[0026] On its bottom face on the counter-bearing side, elastomer spring1 comprises a bottom plate 16 and is connected with same in amaterial-fitting manner. Said bottom plate 16 being in turn connectedform-fittingly, if the case may be, in addition material-fittingly withcounter-bearing 3.

[0027] On the load-receiving surface 8 of elastomer spring 1, a dome 9is integrally formed from the matrix elastomer of elastomer spring 1 asa centering pin for helical spring 2. The centering pin is tapered atits bearing side end and therefore comprises insertion shoulders 17facilitating the insertion of dome 9 and elastomer spring 1 into helicalspring 2 when the bearing is being assembled.

[0028] Dome 9 comprises on its bearing side an open recess 18 extendingthroughout the entire centering pin 9 until deep into elastomer spring1.

[0029] Recess 18 serves for reducing the spring rigidity of elastomerspring 1 in the radial direction, since it reduces the push surface ofelastomer spring 1 and hence the readjustment force of elastomer spring1 in the radial direction.

[0030] The simultaneously arising and undesired weakening of centeringpin 9 caused by recess 18, is compensated by sheet metal 10 configuredappropriately counter-acting. Sheet metal 10 is comprised of a plane,annulus disc-shaped portion and a central cylindrical portion 19 throughwhich extends recess 18 into elastomer spring 1.

1. Elastomer spring for supporting an axially aligned helical spring in series connection, with said helical spring, particularly comprised of spring steel, being axially loadable as provided under static and dynamic pressure characterized by a laterally yielding adjustment matched by way of configuration and dimensioning of the elastomer spring (1) as a transverse load spring.
 2. Elastomer spring according to claim 1, characterized by a reduction of the radial spring rigidity of the transverse load spring (1) by an increase of the axial height of the transverse load spring, a reduction of the hardness of the elastomer of the transverse load spring, and a formation of recesses (18) and cavities in the matrix of the transverse load spring (1).
 3. Elastomer spring according to any one of claim 1 or 2, characterized by a setting of the ratio axial rigidity/radial rigidity of the series connection of a helical steel spring (2) and the transverse load spring (1) to values in the range from 1:1 to 30:1.
 4. Elastomer spring according to any one of claims 1 through 3, characterized by a surface-complementary configuration of the radial faces (8) of the transverse load spring body (1) and the supporting surface of helical spring (2) at an over dimensioning of the peripherally and circumferentially configured radial faces of the transverse load spring body according to the size of one helical spring wire diameter.
 5. Elastomer spring according to any one of claims 1 through 4, characterized by a profiled sheet metal (10) incorporated into the elastomer spring by way of vulcanization directly below the load-receiving surface (8) of elastomer spring (1) and plane-parallel to same and completely enclosed by the spring elastomer, the surface of which profiled sheet metal (10) is configured shape-complementary to the supporting surface of helical spring (2) and is dimensioned at least slightly larger than same.
 6. Elastomer spring according to any one of claims 1 through 5, characterized by a dome (9) formed on the load-receiving surface (8) of elastomer spring (1) as a centering pin for helical spring (2).
 7. Elastomer spring according to claims 5 and 6, characterized by a sheet metal (10) entirely incorporated by way of vulcanization, the contour of which also follows the three-dimensional contour of elastomer dome (9).
 8. Elastomer spring according to any one of claims 1 through 7, characterized by a cavity aligned coaxially to the longitudinal axis of helical spring (2) or a recess (18) in the elastomer spring matrix, which recess (18) is aligned coaxially to the longitudinal axis of the helical spring (2) and is also open through a sheet metal (10) towards the helical spring.
 9. Elastomer spring according to any one of claims 1 through 8, characterized by a bottom plate (16) being all-over and material-fittingly connected with the bottom surface opposite the load-receiving surface (8) of elastomer spring (1).
 10. Elastomer spring according to any one of claims 1 through 9, characterized by an appropriately permissible radial delectability of elastomer spring (1) between the load-receiving surface (8) and the bottom surface of the elastomer spring, which is larger than the height of the elastomer spring body.
 11. Use of an elastomer spring having the features according to any one of claims 1 through 10 for supporting load-bearing helical axial springs in bearings, in particular of unit bearings and unit supports in motor vehicles in a manner relieving from transverse forces. 